Global Positioning System (GPS) technology has become widely used in mobile phones to provide location determination for the mobile/cell phones. GPS technology, however, may be less effective inside buildings and in heavily-built-up urban canyons. Therefore, various technologies have been used to assist GPS technology in difficult-to-cover areas. Some systems, such as Bluetooth and Near-Field Communication (NFC), may be used in limited (e.g., short-range) areas. Other systems, such as Wi-Fi hot spots, may provide longer range than Bluetooth or NFC and have been widely used to assist GPS in location determination.
In using Wi-Fi to assist GPS, a priori mapping of Wi-Fi hot spots may be carried out either through (a) drive tests or (b) crowd-sourcing. In the case of (a) drive tests, a test van may drive through the streets and collect a given Wi-Fi hot spot's location and identifier information. In the case of (b) crowd-sourcing, these functions may be carried out by the mobile/cell phone users that form the crowd. For example, a mobile/cell phone may collect the Wi-Fi hot spot's location and identifier information, and may transmit the location and identifier information via a cellular network to a central database where it can be used in the future. Both the (a) drive-testing approach and the (b) crowd-sourcing approach may have drawbacks, however.
Examples of such drawbacks include:                1. A mobile/cell phone that wants to determine its location may have to collect the Wi-Fi hot spot's identifier (or the identifiers of multiple nearby hot spots) and then transmit the identifier(s) via a cellular network to the central database. The central database then calculates the location, and transmits it to the mobile/cell phone via the cellular network. This process may take away from cellular network resources (e.g., network signaling resources). As such usage increases, this can be a significant burden on the cellular network resources.        2. A database (e.g., the central database) of Wi-Fi hot spots may need to be maintained over time. If maintenance of the database is performed using drive tests, then it may be a manual, cumbersome, and costly process. If it is performed using crowd-sourcing, then it may take away from cellular network resources.        3. Crowd-sourcing techniques may generate privacy concerns. Although such concerns can be addressed to some extent by a database administrator, privacy can still be subject to abuse.        4. None of these approaches addresses sudden changes in the locations of Wi-Fi hot spots. Such changes can occur naturally as users move their Wi-Fi hot spots without notice and at any time. This problem may become quite significant as Wi-Fi hot spots become more portable. Although this may not be very common, it is expected that Wi-Fi hot spots may be moved to obtain additional range because the range provided with a mobile/cell phone may be limited due to transmit power.        